How to combine this MySQL queries? - mysql

Question

I have 2 tables like this:
table:prices
id, project_id, real_min_price, real_max_price
1 | 100100 | 500 | 2000
2 | 100100 | 900 | 3000
3 | 100100 | 2500 | 3200
4 | 100100 | 320 | 3900
table:gifts
id, project_id, min_price, max_price, gift
1 | 100100 | 0 | 1000 | 10
2 | 100100 | 1001 | 2000 | 20
3 | 100100 | 2001 | 3000 | 30
4 | 100100 | 3001 | 4000 | 40
5 | 100100 | 4001 | 5000 | 50
6 | 100100 | 5001 | 6000 | 60
$ID = 100100;
// find highest price
SELECT MAX(real_max_price) FROM `prices` WHERE project_id='$ID';
$MAX_PROJECT_PRICE = $dbo->getOne();
-- returns 3900
// find the limit row which between min-max columns of this value
SELECT gift FROM `gifts` WHERE project_id='$ID'
AND max_price>='$MAX_PROJECT_PRICE' ORDER BY max_price ASC LIMIT 1;
$MAX_GIFT = $dbo->getOne();
-- founded 4th row of the gifts table and returns 40
// remove other gift rows higher then MAX_GIFT value
DELETE FROM `gifts` WHERE project_id='$ID' AND gift>'$MAX_GIFT';
-- deleted 5th and 6th rows.
in this scenario
it will find max price as "3900" so, 5th and 6th row of gifts table will be removed.
but this way is really bad, it should be done in one query but how?

Answer 1

Okay you can except delete query, at least maybe we can combine first
2 queries to find MAX_GIFT value.
To combine the first two queries you can do.
Query
SELECT
gift
FROM
gifts
WHERE
project_id = 100100
AND max_price >= (SELECT MAX(real_max_price)
FROM prices
WHERE project_id = 100100;)
ORDER BY
max_price ASC
LIMIT 1;
And using all three queries into one.
Query
DELETE FROM
gifts
WHERE
project_id = 100100
AND
gift > (SELECT
gift
FROM
gifts
WHERE
project_id = 100100
AND
max_price >= (SELECT
MAX(real_max_price)
FROM
prices
WHERE
project_id = 100100;
)
ORDER BY
max_price ASC
LIMIT 1
)

Answer 2

Here is a solution to run the delete command based on your queries conditions:
delete from gifts where gift in
(
select gift from
(
select gift, #row:=#row+1 as rw
from gifts, (select #row:=0) a
where (select max(real_max_price)
from prices
where project_id=100100 limit 1) < max_price
and project_id = 100100
order by gift
) sub
where rw>1
);
Sample data and test.
create table prices (
id integer,
project_id integer,
real_min_price integer,
real_max_price integer
);
create table gifts (
id integer,
project_id integer,
min_price integer,
max_price integer,
gift integer
);
insert into prices values
(1,100100,500,2000),
(2,100100,900,3000),
(3,100100,2500,3200),
(4,100100,320,3900);
insert into gifts values
(1 , 100100 , 0 , 1000 , 10),
(2 , 100100 , 1001 , 2000 , 20),
(3 , 100100 , 2001 , 3000 , 30),
(4 , 100100 , 3001 , 4000 , 40),
(5 , 100100 , 4001 , 5000 , 50),
(6 , 100100 , 5001 , 6000 , 60);
Running the query I provided you will get on your gifts table.
1 100100 0 1000 10
2 100100 1001 2000 20
3 100100 2001 3000 30
4 100100 3001 4000 40